U.S. patent number 8,600,545 [Application Number 12/975,774] was granted by the patent office on 2013-12-03 for system and method for inspecting and sorting particles and process for qualifying the same with seed particles.
This patent grant is currently assigned to Titanium Metals Corporation. The grantee listed for this patent is Matthew R. Earlam. Invention is credited to Matthew R. Earlam.
United States Patent |
8,600,545 |
Earlam |
December 3, 2013 |
System and method for inspecting and sorting particles and process
for qualifying the same with seed particles
Abstract
A method for qualifying an automated process for inspecting and
sorting particles through the production and use of seed particles
is disclosed. In one embodiment, seed particles are produced by
forming a conformal surface layer on a plurality of particles,
thereby imparting them with at least one property whose value or
range of values is the same as or about the same as a value or
range of values of a corresponding property of undesirable
particles. By introducing a predetermined quantity of seed
particles, their detection and removal by the automated sorting
system can be used to periodically calibrate and qualify the
sorting system without interrupting the manufacturing operations or
introducing actual undesirable particles into the process stream.
The production and use of seed particles to qualify an automated
sorting system is particularly well-suited for use with Ti sponge
sorting operations.
Inventors: |
Earlam; Matthew R. (Henderson,
NV) |
Applicant: |
Name |
City |
State |
Country |
Type |
Earlam; Matthew R. |
Henderson |
NV |
US |
|
|
Assignee: |
Titanium Metals Corporation
(Exton, PA)
|
Family
ID: |
46314472 |
Appl.
No.: |
12/975,774 |
Filed: |
December 22, 2010 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20120165973 A1 |
Jun 28, 2012 |
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Current U.S.
Class: |
700/223; 700/228;
702/38; 700/222; 702/35 |
Current CPC
Class: |
B07C
5/3425 (20130101); B07C 5/00 (20130101) |
Current International
Class: |
G06F
7/00 (20060101); G01B 5/28 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0574831 |
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Sep 1999 |
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EP |
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63157044 |
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Jun 1988 |
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JP |
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8015031 |
|
Jan 1996 |
|
JP |
|
WO 97/09689 |
|
Mar 1997 |
|
WO |
|
WO 00/50181 |
|
Aug 2000 |
|
WO |
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WO 2009/019605 |
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Feb 2009 |
|
WO |
|
Other References
Swanson, et al. in "A Real-Time Coal Content/Ore Grade (C2OG)
Sensor," published online at
http://www.osti.gov/energycitations/product.biblio.jsp?osti.sub.--id=7917-
09 in Apr. 2005. cited by applicant .
Weldon Solutions brochure on "Quality Control Robot for Removal of
Metal Impurities," published online at
http://www.weldonmachinetool.com/downloads/profiles-fall09.pdf in
the Fall of 2009. cited by applicant .
P.H. Heinemann in "Machine Vision Inspection of `Golden Delicious`
Apples," Applied Engineering in Agriculture, vol. 11, No. 6, pp.
901-906 (1995). cited by applicant .
Y. Tao, et al. in "Machine Vision for Color Inspection of Potatoes
and Apples," Transactions of ASAE, vol. 38, No. 5, pp. 1555-1561
(1995). cited by applicant .
Tom Pearson in "Machine Vision System for Automated Detection of
Stained Pistachio Nuts," SPIE, vol. 2345, pp. 95-103 (1995). cited
by applicant .
J.-L. Delplancke, et al. in "Self-Colour Anodizing of Titanium,"
Surface Technology, 16 pp. 153-162 (1982). cited by applicant .
A. Rosenfeld, et al. in "Sorting of Aluminum Alloy Scrap by Laser
Induced Optical Emisssion Spectroscopy," Third International
Symposium on Recycling of Metals and Engineered Materials, Edited
by P.B. Queneau and R.D. Peterson, The Minerals, Metals &
Materials Society, pp. 751-763 (1995). cited by applicant .
Key Technology, Inc. article entitled "Understanding How Electronic
Sorting Technology Helps Maximize Food Safety," published online at
http://www.key.net/files/downloads/how-electronic-sorting-technology-help-
s-max-food-safety.pdf in Jun. 2010. cited by applicant .
PCT Notification of Transmittal of the International Search Report
and the Written Opinion of the International Searching Authority,
or the Declaration dated May 3, 2012 corresponding to International
Application No. PCT/US11/66803. cited by applicant.
|
Primary Examiner: Jones; Yolanda
Attorney, Agent or Firm: Locke Lord LLP Fallon; Peter J.
Claims
What is claimed is:
1. A method for qualifying an automated system for inspecting and
sorting particles, seed particles, and undesirable particles
comprising: forming a conformal surface layer on the particles to
produce coated seed particles to impart at least one property with
a value or range of values that is the same as or about the same as
a value or range of values of a corresponding property of
undesirable particles; calibrating the system to identify or
distinguish between particles, seed particles and undesirable
particles according to a predetermined property value or range of
property values; introducing a predetermined quantity of the seed
particles to a process stream comprising a plurality of particles
and undesirable particles; monitoring the process stream as it is
transported along a moving surface; identifying the seed particles
and the undesirable particles in the process stream; removing the
undesirable particles and the seed particles from the process
stream; determining whether the number of seed particles removed is
equal to the predetermined quantity of seed particles which were
introduced to the process stream; and recalibrating the system to
maximize the removal of undesirable particles from the process
stream based upon the determining result.
2. The method of claim 1 wherein the surface layer is formed by at
least one process selected from the group consisting of
anodization, electroplating, chemical vapor deposition physical
vapor deposition, and painting.
3. The method of claim 1 wherein the conformal surface layer is
formed from a material which does not undesirably influence the
properties of articles manufactured using the particles.
4. The method of claim 3 wherein the particles are comprised of Ti
sponge, the undesirable particles are comprised of nitrided Ti
sponge and the seed particles are comprised of Ti sponge, wherein
the surface of the seed particles is coated with a conformal layer
of a material having at least one property with a value or range of
values that is the same as or about the same as a value or range of
values of a corresponding property of nitrided Ti sponge.
5. The method of claim 4 wherein the seed particles are comprised
of Ti sponge having a conformal surface layer of titanium oxide
formed thereon with the thickness of the titanium oxide layer being
adjusted to provide the seed particles with a color or range of
colors that is the same or about the same as a corresponding color
value or range of color values of nitrided Ti sponge.
6. The method of claim 5 wherein the color value or range of color
values of the seed particles is gold, yellow, brown, black, blue,
red, violet or shades and/or combinations of these colors.
Description
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates generally to a process for sorting
particles. In particular, the present invention relates to a
process for qualifying an automated system for inspecting and
sorting particles by introducing a predetermined number of seed
particles into the process stream. This invention also relates to
the production and qualification of seed particles having at least
one property whose value or range of values is the same as or about
the same as a value or range of values of a corresponding property
of known undesirable particles.
II. Background of the Related Art
Conventional mining and/or metal processing operations can involve
an intermediate stage wherein fragments or particles of the desired
ore or metal are transported along a moving surface for visual
inspection and the removal of undesired impurities. Removal of
impurity fragments or particles is important for applications in
which tight elemental concentration tolerances are necessary to
ensure that the material properties of the finished product are
suitable for their intended use. In many cases, such impurities
will have an appearance that is clearly distinct from standard ore
or metal particles having the targeted composition, thereby
enabling their visual identification and removal by human
operators.
Titanium (Ti) is an example of a material which, for applications
involving highly stressed components, requires visual inspection
and sorting during production. Commercial processes, which are used
to extract Ti from TiO.sub.2 and/or TiCl.sub.4, produce a
sponge-like material known as Ti sponge which is then consolidated
into the desired shape by remelting. Under certain conditions, the
production of Ti sponge results in the formation of sponge
particles which have been "burned" and subsequently converted to
titanium oxide or titanium nitride. The incorporation of nitrided
Ti sponge particles during remelting is undesirable because if they
survive the melting phase their presence in the finished metal,
alloy or manufactured product can lead to the formation of hard
alpha material or low density inclusions. These inclusions, if
undetected by various quality checks, can impact the effectiveness
of the manufactured article. Nitrided or oxidized Ti sponge
particles have an appearance which is distinctly different from
that of normal Ti sponge, being a darker shade of color which is
readily discernible to the naked eye. This distinction permits the
identification of the undesired particles and their removal from
the process stream by a human operator.
Current industry standards generally require that the Ti sponge
used to fabricate certain end use components be subject to 100%
visual inspection. However, the use of individual operators to
inspect and sort the process stream can be a time consuming,
labor-intensive and costly process since the moving surface
typically must move slowly to facilitate inspection and removal of
undesired particles by human operators.
Recent approaches to modernizing sorting processes have involved
the implementation of automated sorting systems which are capable
of automatically inspecting and sorting particles in a process
stream. An example of such a system is set forth in U.S. Pat. No.
6,043,445 to Gigliotti, et al. (hereinafter "Gigliotti") which is
directed to an apparatus for color-based sorting of titanium sponge
particles. In one embodiment, Gigliotti discloses the use of an
imaging device to capture a color image of the product as it is
transported on a moving surface. The image is converted to a color
signal and is sent to a central processing unit where the signal is
transformed to a color value. This color value is then compared to
a look-up table which defines acceptable threshold levels. If the
color value is identified as being outside an acceptable range,
then the system identifies particles having this color value as
undesirable product and signals for their removal from the process
stream. The rejected particles may be removed by correlating their
movement along the moving surface with image acquisition such that
the location of the rejected particles can be precisely identified
and their removal effectuated by physical means.
An analogous automated system which is capable of sorting scrap
metal particles based upon their color has been disclosed by U.S.
Pat. No. 5,676,256 to Kumar, et al. ("Kumar"). Yet another approach
to automated inspection is provided by U.S. Pat. No. 5,519,225 to
Mohr, et al. ("Mohr") which describes the use of radiographic
inspection methods to examine particles in a process stream. Mohr
discloses the use of a dual radiation source to alternatively
irradiate particles in the process stream with neutrons and X-rays
or gamma rays and a dual modality gas ionization detector to detect
the radiation after it has passed through the particles. The
detected radiation is processed and displayed on a monitor,
enabling objects formed with different attenuating materials to be
distinguished. The Gigliotti, Kumar, and Mohr patents are
incorporated by reference in their entirety as if fully set forth
in this specification.
Despite the cost savings and improved sorting capabilities
attainable through the use of automated inspecting and sorting
systems, there has been considerable resistance to their widespread
adoption primarily due to uncertainties associated with the
accuracy, reliability and qualification of these systems. For
example, the performance of automated inspecting and sorting
systems may deviate from the norm due to issues such as nonuniform
illumination of the particles, errors occurring during image
acquisition and/or mechanical problems during sample transport.
In addition, repeated verification and calibration of automated
sorting systems is typically necessary to ensure that the sorting
process is functioning properly. These processes can result in
significant down time since they typically require that the process
flow be stopped so that calibration procedures may be performed
without inadvertently allowing undesirable particles to pass
through the system and be introduced into the manufactured article.
There is therefore a continuing need for the development of
automated inspecting and sorting systems which have improved
consistency and reliability, operate at reduced cost and can be
accurately verified and calibrated with minimal interruption of the
process flow.
SUMMARY OF THE INVENTION
In view of the above-described problems, needs, and goals, systems
and methods of qualifying an automated inspecting and sorting
system using seed particles are disclosed. In one embodiment a
method of forming and qualifying seed particles for use in
automated inspecting and sorting systems is provided. In a
particular embodiment, the seed particles are formed by initially
producing a plurality of particles having a predetermined shape and
size distribution. A conformal surface layer is then formed on the
particles to produce seed particles and thereby impart to the seed
particles at least one property with a value or range of values
that is the same as or about the same as a value or range of values
of a corresponding property of undesirable particles. A plurality
of the seed particles are added to a process stream comprising the
plurality of particles which is processed by the automated
inspecting and sorting system. The automated inspecting and sorting
system is programmed to detect and selectively remove from the
process stream those seed particles having a predetermined property
value or range of property values. The seed particles which are
detected and removed from the process stream are retained and used
to qualify the automated inspecting and sorting system itself
during standard startup and operating conditions.
In some embodiments, metal particles are used having an average
diameter of about 2 mm, about 3 mm or about 4 mm. The conformal
surface layer formed on the metal particles may be produced using
deposition processes which include, but are not limited to at least
one of anodization, electroplating, chemical vapor deposition,
physical vapor deposition and painting. The deposition of a
conformal surface layer produces seed particles having at least one
property with a value or range of values that is the same as or
about the same as a value or range of values of a corresponding
property of undesirable particles. In one embodiment, the conformal
surface layer provides the seed particles with a color or range of
colors which is the same or about the same as a corresponding color
value or range of color values of the undesirable particles. In a
particular embodiment, the conformal surface layer is formed using
a material which does not adversely affect the properties of
products manufactured from the particles. In some embodiments, the
seed particles that are not rejected are reintroduced to the
automated inspecting and sorting system.
In another particular embodiment, the particles are comprised of Ti
sponge, the undesirable particles are comprised of nitrided Ti
sponge and the seed particles are comprised of Ti sponge, wherein
the surface of the seed particles is coated with a conformal layer
of a material having at least one property with a value or range of
values that is the same as or about the same as a value or range of
values of a corresponding property of nitrided Ti sponge. In an
even more particular embodiment, the seed particles are comprised
of Ti sponge particles having a conformal surface layer of titanium
oxide formed thereon. The thickness of the titanium oxide layer may
be adjusted to provide the seed particles with a color or range of
colors that are the same or about the same as a corresponding color
value or range of color values of nitrided Ti sponge. In some
embodiments, the color value or range of color values of the coated
seed particles is gold, yellow, brown, black, blue, red, violet, or
shades and/or combinations of these colors.
In another embodiment, a method for qualifying an automated system
for inspecting and sorting particles, seed particles and
undesirable particles is provided. The method involves producing
seed particles having at least one property with a value or range
of values that is the same as or about the same as a value or range
of values of a corresponding property of undesirable particles and
calibrating the system to identify or distinguish between
particles, seed particles and undesirable particles according to a
predetermined property value or range of property values. A
predetermined quantity of the seed particles are introduced to a
process stream comprising a plurality of particles and undesirable
particles and the process stream is monitored as it is transported
along a moving surface. The seed particles and undesirable
particles present in the process stream are identified and then
removed from the process stream. It is then determined whether the
number of seed particles removed is equal to the predetermined
quantity of seed particles which were introduced to the process
stream, and the system is recalibrated to maximize the removal of
undesirable particles from the process stream based upon the
determining result.
In another embodiment, the present invention relates to a metal
produced from metal particles which have been inspected using an
automated system for inspecting and sorting metal particles which
has been qualified using seed particles. In a particular
embodiment, the metal comprises Ti produced from Ti sponge which
has been sorted using an automated inspecting and sorting system
that has been qualified using Ti seed particles. In yet another
embodiment, the present invention relates to a manufactured product
formed from a metal produced from metal particles which have been
inspected using an automated system for inspecting and sorting
metal particles that has been qualified using seed particles.
In yet another embodiment, a system for inspecting and sorting
particles, seed particles and undesirable particles is disclosed.
In a particular embodiment, the system comprises a plurality of
particles having a predetermined shape and size distribution,
wherein a conformal surface layer is formed on a plurality of the
particles to produce seed particles having at least one property
whose value or range of values is the same as or about the same as
a value or range of values of a corresponding property of an
undesirable particle; a process stream comprising particles, seed
particles and undesirable particles to be inspected and sorted; and
a first automated inspecting and sorting apparatus.
An embodiment of the first automated inspecting and sorting
apparatus comprises a feeder for introducing a process stream into
the apparatus at a predetermined feed rate, a moving surface for
transporting the process stream through the system, a lamp for
illuminating the process stream as it is transported along the
moving surface, a camera for acquiring images of the process
stream, a device for analyzing images acquired by the camera and
comparing the images with a pre-determined range of values for
particles, seed particles and undesirable particles, and an air
ejector for removing seed particles and undesirable particles from
the process stream. In a particular embodiment the seed particles
and undesirable particles which are removed from the process stream
by the system for inspecting and sorting particles are sent back to
the feeder.
In one embodiment, the system for inspecting and sorting particles,
seed particles and undesirable particles comprises a second
automated inspecting and sorting apparatus. In this embodiment,
seed particles and undesirable particles that were removed from the
process stream by the first automated inspecting and sorting
apparatus are inspected and sorted by the second automated
inspecting and sorting apparatus. In another particular embodiment,
the feed rate of the first automated inspecting and sorting
apparatus is higher than the feed rate of the second automated
inspecting and sorting apparatus.
The production of seed particles and their use to qualify an
automated system for inspecting and sorting particles provide a
means for quickly and reliably ensuring that such sorting systems
are functioning according to their intended use. The use of seed
particles to qualify an automated inspecting and sorting system has
the advantage of providing a more accurate, efficient, and
cost-effective sorting system which, in turn, provides increased
confidence that the sorted product contains fewer undesirable
particles than that inspected by a human operator.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated into and
constitute part of this disclosure, illustrate exemplary
embodiments of the disclosed invention and serve to explain the
principles of the disclosed invention.
FIG. 1 is a schematic showing the components of an exemplary
automated inspecting and sorting system.
FIG. 2 is a flowchart illustrating the sequence of steps used to
produce and qualify seed particles.
FIG. 3 is a flowchart illustrating an exemplary method of
qualifying an automated inspecting and sorting system using seed
particles.
FIG. 4 is a flowchart showing an exemplary method of sorting
particles using a plurality of automated inspecting and sorting
systems.
FIG. 5 is a flowchart showing another exemplary method of sorting
particles using a plurality of automated inspecting and sorting
systems.
FIG. 6A shows exemplary Ti sponge particles which have been
anodized in a solution of 10% sodium bicarbonate in water at 52
volts for 20 minutes.
FIG. 6B shows exemplary Ti sponge particles which have been
anodized in a solution of 10% sodium bicarbonate in water at 22
volts for 20 minutes.
FIG. 7 is a plot comparing the recovery rate of Ti seed particles
as a function of size, color and sorting method.
Throughout the drawings, the same reference numerals and characters
are used to denote like features, elements, components or portions
of the illustrated embodiments unless otherwise stated. While the
disclosed invention is described in detail with reference to the
figures, it is done so in connection with the illustrative
embodiments.
DETAILED DESCRIPTION OF THE INVENTION
Exemplary methods for qualifying an automated inspecting and
sorting system using seed particles are disclosed. Embodiments of
methods for producing and qualifying the seed particles themselves
are also disclosed. The production of seed particles having at
least one property whose value or range of values is the same as or
about the same as a value or range of values of a corresponding
property of undesirable particles permits their use as mock
undesirable particles in an actual process stream which is subject
to an automated inspecting and sorting system. By using seed
particles as mock undesirable particles, the system itself can be
periodically qualified by introducing a predetermined quantity of
seed particles at random intervals during actual operation of the
system. An analysis of whether these particles were detected by the
system can be used to verify and fine-tune the inspecting and
sorting process.
Within this specification, a property of the particles is
understood to be any material property which includes, but is not
limited to, the size, shape, density, surface texture, color, or
composition of the particles. Furthermore, each property can be
assigned a given value. For example, and not to be limiting, a
property value for size or shape may include the numerical value of
one or more external dimensions, a property value for the density
would be a measurement of mass per unit volume, a property value
for color may include a particular color, a HEX value, or RGB
value, a property for surface texture may include smooth, rough, or
jagged and the property value of composition may include the type
and amounts of the elemental constituents of the particle. In some
embodiments one or more properties of the particles may be measured
using, for example, an image acquisition device such as a camera or
through specialized techniques such as optical emission
spectroscopy (OES) or X-ray fluorescence (XRF). It is to be
understood that any reference to a "property of an undesirable
particle" within this specification refers to the specific value of
the property which is distinguishable from the value of an
acceptable particle.
The seed particles may be produced using a material which, if it
were to inadvertently pass through the inspection system and be
incorporated into the final product, does not have an undesirable
effect on the properties of the resulting product. Use of an
acceptable material to produce the seed particles permits
introduction of the seed particles directly into an actual
production line so that periodic qualification of the sorting
system can be performed during system start-up or actual sorting
operations. The use of seed particles is particularly advantageous
when used with processes which sort metal particles and/or their
ores since it frequently is the case that variations in composition
are readily visible as differences in color, structure, or some
other visual property of the metal or ore. By identifying this
distinction either by use of human operators or with an automated
inspecting and sorting system, undesirable particles can be removed
from the process stream.
Since the characteristics of undesirable particles are known, a
property that does not have an undesirable impact on the
performance of the particles can be deliberately imparted to known
acceptable particles which then serve as seeds that are used to
test the inspecting sorting capabilities of the system. For
example, if the undesirable particles have a color which is
distinct from that of particles having the desired composition, a
thin conformal layer can be formed on one or more particles such
that they take on the color of a undesirable particle. Within this
specification a conformal layer is defined as a surface layer which
is applied to or formed upon all exposed surfaces of a particle
such that it covers substantially the entire exterior of the
particle. In a particular embodiment, the entire surface of the
particle is covered such that no uncoated regions are visible;
however, a completely covered surface is not a necessary criteria.
In alternative embodiments, the particle may be provided with a
surface coating which covers a fraction of the exposed surface area
sufficient to provide the particle with a color which is the same
or about the same as undesirable particles and permits its
detection by the automated inspecting and sorting system. In one
embodiment, the fraction of the particle's surface that is covered
by a surface coating ranges from about 80% up to about 100% of the
exposed surface area.
The color of a seed particle is determined to be the same as that
of an undesirable particle when the color shade or value of the
seed particle identified by the automated inspecting and sorting
system is the same or about the same as the color shade or value of
the undesirable particle. That is, a seed particle and undesirable
particle are determined to have the same color when, after being
imaged by the automated inspecting and sorting system, they are
shown to have the same or about the same color shade or value. It
is, however, to be understood that the surface layer is not limited
to providing a color to the particles, but may impart to the seed
particle any property which is characteristic of undesirable
particles. For example, in one embodiment particles may be
distinguished based upon their density or their emission of
secondary X-rays during X-ray irradiation as in the case of XRF. In
another embodiment, particles may be distinguished by OES and, in
an even more particular embodiment, by laser-induced OES as
described, for example, by A. Rosenfeld, et al. in "Sorting of
Aluminum Alloy Scrap by Laser Induced Optical Emission
Spectroscopy," Third International Symposium on Recycling of Metals
and Engineered Materials, The Minerals, Metals & Materials
Society, pp. 751-763 (1995) which is incorporated by reference in
its entirety as if fully set forth in this specification.
The surface layer is preferably formed of a material which does not
have an undesirable effect on any products manufactured from the
metal particles. An undesirable effect occurs when the inclusion of
a material, whether intentional or inadvertent, causes the
properties of the resulting product to be changed in an undesirable
way. For example, if the mechanical properties of a ceramic,
polymer, metal, alloy or manufactured product such as the ultimate
tensile strength, tensile yield strength, elongation or fatigue
resistance are unintentionally reduced due to the inclusion of the
material, then it is said to have a undesirable effect on its
properties. Such an undesirable effect is not limited to the
properties listed above, but may also include any alteration of the
microstructure, composition or other material property in an
unintended way as a result of the inclusion of the material. Within
this specification, the inclusion of nitrogen in a Ti alloy is
considered to have an undesirable effect on the resulting
properties if it is present in an amount greater than 0.1 weight
percent (wt. %).
Although the production and use of seed particles is beneficial for
sorting essentially any type of material such as, for example,
ceramics, polymers, metals or ores, it is particularly well suited
for sorting Ti sponge particles. Although this disclosure is not
intended to be limited to Ti, the embodiments disclosed and
described within this specification will be made with reference to
systems for sorting Ti sponge particles due to the advantages an
automated system affords to the Ti sponge sorting process.
During manufacturing operations, the surface of some Ti sponge
particles may become oxidized or nitrided and, when this occurs,
the Ti sponge is typically referred to as "burnt" Ti sponge. The
presence of burnt Ti sponge in the process stream is undesirable
because if it survives the melting phase its inclusion in
subsequent metals, alloys or manufactured products may lead to the
formation of hard alpha material or low density inclusions. These
inclusions, if undetected by various quality checks, have an
undesirable effect on the material properties of the finished
product. Conventional Ti sponge has a silver or dull gray color,
but the incorporation of nitrogen provides the titanium sponge
particles with a distinctive gold, yellow, brown, black, blue, red
or violet color.
When a batch is found to contain burnt Ti sponge, samples are
typically chemically tested to determine whether nitrogen is
present. If the nitrogen content is found to be higher than
approximately 0.1 wt. %, the batch cannot be used for some specific
applications. It is preferable that nitrided Ti sponge particles be
removed from the process stream prior to remelting because of the
undesirable effects nitrided Ti may have on the properties of a Ti
alloy.
Identification and removal of burnt Ti sponge may be accomplished
by manual or automated processes. Although the former is more
time-consuming and costly, it is a method which is more well-known
and is generally accepted in the industry. Human inspectors can be
subject to some type of qualification process which may include,
but is not limited to, testing the inspector's color vision and
recognition of burnt Ti and/or foreign matter in the process
stream. The use of automated inspecting and sorting processes offer
the advantages of speed, lower operating costs and flexibility;
however, it is difficult to ascertain their continued operation at
acceptable detection levels and to verify that different systems
function identically. In order to facilitate their adoption within
the industry, it is necessary to demonstrate that an automated
inspecting and sorting system can be both quick and
inexpensive.
Within this disclosure, the basic components of an automated system
for inspecting and sorting particles are described. A description
of methods of producing and qualifying seed particles having at
least one property whose value or range of values is the same as or
about the same as a value or range of values of a corresponding
property of undesirable particles is also described as well as the
process of using the seed particles to qualify an automated
inspecting and sorting system. Exemplary embodiments describing the
formation, qualification, and use of actual Ti seed particles to
qualify an automated inspecting and sorting system are
disclosed.
I. Automated Inspecting and Sorting Systems
A number of color-based inspecting and sorting systems which have
been adapted to sort metal particles are well-known in the art. An
example is the Machine Vision system which has traditionally been
used to inspect and sort a wide variety of products in the food
industry. Some examples describing the use of Machine Vision
systems are provide by P. H. Heinemann in "Machine Vision
Inspection of `Golden Delicious` Apples," Applied Engineering in
Agriculture, Vol. 11, No. 6, pp. 901-906 (1995) as well as by Y.
Tao, et al. in "Machine Vision for Color Inspection of Potatoes and
Apples," Transactions of ASAE, Vol. 38, No. 5, pp. 1555-1561 (1995)
and by Tom Pearson in "Machine Vision System for Automated
Detection of Stained Pistachio Nuts," SPIE, Vol. 2345, pp. 95-103
(1995). Each of the aforementioned are incorporated by reference in
their entirety as if fully set forth in this specification. An
exemplary system for inspecting and sorting Ti sponge particles on
the basis of color has been previously disclosed by Gigliotti
whereas a system for inspecting and sorting scrap metal by color
has been provided by Kumar.
Automated inspecting and sorting systems such as the Machine Vision
system can be tailored to inspect and sort a process stream based
upon the color of the individual particles. The inspecting and
sorting process is accomplished using a color imaging system which
identifies particles that are different from the majority. A
proprietary software program is used to teach the system an
acceptable color range for the particles. Any particle which is
identified as having a color outside this predetermined range is
categorically rejected. Within this specification, the terms
"color" and "color value" are used interchangeably and are
understood to have equivalent meanings. The particles themselves
may be sorted using, for example, air jets, a mechanical arm with a
suction cup on one end or some type of manipulator to manually
remove the rejected particles.
A side view of a schematic showing the primary components of an
exemplary inspecting and sorting system (100) which is known in the
art is provided in FIG. 1. A loss-in-weight feeder (1) introduces
particles along the full width of a moving surface (3) such as a
conveyor belt through a feeder discharge chute (2). The feeder
discharge chute (2) is designed to accelerate the particle feed
such that it is evenly distributed over the exposed surface area.
In one embodiment, the feeder discharge chute (2) creates a
particle coverage amounting to approximately 25% of the exposed
surface area. The moving surface (3) itself typically transports
particles at a speed of, for example, approximately 480 feet per
minute (ft/min). The conveyance speed can, however, be adjusted as
needed in order to optimize the sorting process.
An upper high-intensity lamp (4) illuminates the particles as they
are transported along the moving surface (3) whereas an upper line
scan camera (5) acquires an image of the process stream as it
passes a fixed point. The upper line scan camera (5) may be any
suitable camera as is well-known in the art, but in a particular
embodiment is comprised of 1024 pixels and is capable of high
frequency scans. A bottom line scan camera (7) and bottom
high-intensity lamp (8) are also provided to illuminate and acquire
an image of the underside of the particles. The upper line scan
camera (5) looks down on the moving surface (3) and, hence,
acquires images with the moving surface (3) provided as a backdrop
whereas the bottom line scan camera (7) looks up through the
process stream and typically acquires images against a blue light
emitting diode (LED) background.
Undesirable particles which are identified as having a color that
falls outside the acceptable range are ejected by means of an air
ejector (6) which, in one embodiment, is comprised of a plurality
of nozzles spread out along the full width of the moving surface
(3). In one embodiment the nozzles are spaced approximately
one-fourth of an inch apart. When the location of an undesirable
particle is identified, its position is ascertained by correlating
the conveyance speed of the moving surface (3) with the distance
between the positions of the upper line scan camera (5) and the air
ejector (6). When a particle reaches the end of the moving surface
(3), its forward momentum would normally transport it over the top
surface of a cutting blade (9). However, when an undesirable
particle has been identified and reaches the end of the moving
surface (3), one or more of the plurality of air ejector (6)
nozzles is activated when its position intercepts that of the
undesirable particle(s). A strong puff of air is emitted from the
targeted air ejector (6) nozzles to direct the undesirable
particle(s) downwards such that they fall below the cutting blade
(9) and are separated from the process stream.
It is to be understood that the inspecting and sorting system (100)
disclosed in this specification and shown in FIG. 1 is merely
exemplary of a plurality of such systems which are known in the art
and may be used to sort particles. Furthermore, the automated
sorting system illustrated in FIG. 1 is not drawn to scale. An
illustration of an exemplary inspecting and sorting system
analogous to that disclosed in this specification may be found in
an article entitled "Understanding How Electronic Sorting
Technology Helps Maximize Food Safety," which was published in June
2010 by Key Technology, Inc. and is incorporated by reference as if
fully set forth in this specification. One feature of the
inspecting and sorting system described in this specification is
its ability to distinguish between objects based upon their color
or color value and then remove from the process stream those
objects whose color or color value falls outside the acceptable
range. Although the particles are distinguished based upon their
color or color value, such sorting systems may be adapted to sort
particles based upon any other distinguishing material property
such as their density, optical emission spectra or X-ray
fluorescence which can be readily measured and analyzed by a
sorting system.
The operation of the sorting system (100) may be tested and
qualified using a set of standards which define the acuity of the
sorting system (100). Although the sorting system's (100)
capabilities can be demonstrated using actual undesirable
particles, the production of seed particles as mock undesirable
particles enables their use during routine setup and under standard
operating conditions. The formation of seed particles is described
in the following section.
II. Production of Seed Particles
One advantage of using seed particles is that while the seed
particles mimic the properties of undesirable particles, products
formed using particles from the process stream are not undesirably
affected by the incorporation of the seed particles When used in a
sorting system (100) which distinguishes particles based upon their
color, the distinguishing property is therefore the color of the
particles.
Another feature of the seed particles is that their shape is such
that they remain stationary while being transported along the
moving surface (3). Any shape may be used so long as it has
sufficient supporting points and/or facets to prevent it from
rolling on the moving surface (3) between the point at which it is
first imaged by the upper line scan camera (5) and when it reaches
the air ejector (6). The particles must remain stationary to ensure
that the undesirable particles scanned by the upper line scan
camera (5) and identified by the system are the same particles that
are subsequently removed from the process stream once they reach
the air ejector (6).
Particles having the desired shape, size and surface features may
be obtained from the process stream so that they may be formed into
seed particles. The average size of the seed particles may be
controlled by crushing and/or grinding the particles and then
passing them through an appropriately sized sieve or mesh. Although
the average size of the particles used to produce the seed
particles is not limited to any specific value or range of values,
in a particular embodiment, for metal particles the average
particle diameter is about 2 mm, about 3 mm or about 4 mm. These
particle sizes are especially suited for use in the production of
Ti sponge seed particles.
A. Formation of a Conformal Surface Layer
A variety of methods may be used to process the selected particles
and produce seed particles having the appropriate color or colors.
In one embodiment, color may be imparted to the particles by
applying a dye or coating of paint having the desired color. The
desired color may be accomplished by conventional spray, brush,
immersion or any other application technique which is well-known in
the art. A disadvantage of this technique is that the paint itself
may be manufactured by a third party and its continued availability
may become an issue. Furthermore, there may be issues associated
with color uniformity between separate batches of paint. Yet
another issue is that the paint coating will be more likely to chip
or wear with repeated handling.
In another embodiment, an ultrathin and conformal film having the
desired color may be formed by thin film deposition processes which
include, but are not limited to anodization, electroplating,
chemical vapor deposition (CVD) and physical vapor deposition
(PVD). Film growth by CVD may be facilitated by the use of
processes which stimulate film growth such as plasma enhanced CVD.
Growth by PVD may be accomplished using deposition techniques which
include, but are not limited to, thermal evaporation, e-beam
evaporation and sputtering. Deposition of a conformal surface
coating using the film growth techniques described above will also
yield a more durable and long-lasting coating which is less likely
to wear with repeated handling and use. These deposition techniques
are well-known in the art and a detailed description thereof will
be omitted.
The material deposited as a conformal thin film preferably provides
the surfaces of the coated particles with a color whose value or
range of values is the same as or about the same as a corresponding
value or range of values of known undesirable particles. The color
may be controlled by varying deposition or application parameters
such as the composition, thickness and/or temperature. In a
particular embodiment, the material used to form the surface layer
does not undesirably influence the properties of any finished
product manufactured using particles obtained from the process
flow. That is, the surface layer produced on the seed particles is
such that if they were to inadvertently bypass the sorting system
and be incorporated into the process stream, their presence would
not impact the properties of the resulting product in an
undesirable manner.
In some embodiments, the seed particles may be coated with an
ultraviolet (UV) paint to "tag" the seed particles such that they
may be distinguished from conventional undesirable particles.
Application of UV paint of various colors such as yellow, green,
blue or red may be used to distinguish between different types of
seed particles. The UV paint is transparent under visible light,
but becomes visible when exposed to an UV light source. By
subjecting the UV painted seed particles to an UV light source such
as a black light, they may be readily identified and distinguished
from normal undesirable particles contained within the process
stream.
For applications involving Ti sponge, the formation of an oxide
layer on the surface of the Ti sponge particles has been discovered
to be an effective way of forming seed particles having a color
whose value or range of values is the same as or about the same as
a corresponding value or range of values of nitrided Ti sponge.
Since oxygen is an element which is typically found in Ti and Ti
alloys, the inclusion of oxidized Ti sponge seed particles into the
process stream typically would not have an undesirable effect on
the properties of the subsequent Ti metal, alloy or finished
product formed using particles from the process stream.
Furthermore, the color of the oxidized Ti sponge particles may be
controlled by varying the thickness of the oxide layer. Changes in
the thickness of the oxide layer produce changes in color due to
the interference of incident and reflected light.
An oxidized Ti layer may be readily deposited onto the surface of a
plurality of Ti sponge particles as a conformal thin film using any
of the processes described above including, but not limited to
anodization, electroplating, CVD and PVD film growth techniques.
From among these, anodization is a comparatively low-cost process
which may be readily adapted for use with Ti sponge particles.
Anodization is also readily reproducible and can produce a range of
colors for testing purposes. The anodization of Ti has been
previously described in detail by, for example, J.-L. Delplancke,
et al. in "Self-Colour Anodizing of Titanium," Surface Technology,
16 pp. 153-162 (1982) which is incorporated by reference in its
entirety as if fully set forth in this specification.
In one embodiment, anodization of Ti sponge particles may be
accomplished by submersing a plurality of particles in an
electrolyte having a predetermined temperature. Exemplary
electrolytes which may be used include sodium bicarbonate or
sulfuric acid. The Ti fragments are allowed to sit on a titanium
plate or pan, a metal cathode is immersed in the electrolyte and a
direct current is applied between the electrodes. The oxide layer
thickness and, hence, the color of the Ti sponge particles may be
controlled by varying parameters which include, but are not limited
to the applied voltage, the type, concentration and temperature of
the electrolyte, as well as the anodization time. A well-defined
set of parameters for anodizing Ti particles can be established and
used to produce a set of standards. In a particular embodiment, Ti
sponge is anodized at room temperature in a solution containing 10%
sodium bicarbonate and water. Anodization may be performed by, for
example, applying a voltage of 52 or 22 Volts (V) for a duration of
10 to 20 minutes until the color of the Ti sponge is the same as
that of burnt Ti sponge samples.
In another embodiment, a sheet or foil of Ti may be anodized to
produce colors whose value or range of values is the same as or
about the same as a corresponding value or range of values of
nitrided Ti sponge. The anodized sheet or foil may then be secured
to the sides of a suitable substrate to produce a coated seed
particle. The substrate may be, for example, a plastic cube or
pyramid having a size analogous to the Ti sponge particles being
inspected. The most useful shapes are those that will remain
stationary during transport on a moving surface. Seed particles
produced in this manner may, however, be useful for the production
of color standards which may be used to periodically test the
settings of the automated sorting system.
In yet another embodiment, seeds comprised of pre-cut samples of Ti
such as a cube or pyramid may have a conformal surface layer formed
thereon. The surface layer imparts a color whose value or range of
values is the same as or about the same as a corresponding value or
range of values of undesirable particles to the pre-cut sample
using any of the processes described above (i.e., anodization,
electroplating, CVD and PVD). Seed particles of this type may be
used to test the settings of an automated sorting system. It is to
be understood that although the production of seed particles in
this section has been described using a Ti sheet, foil or pre-cut
sample as an example it is to be understood that this is merely
exemplary and any of a plurality of other metals or substrates may
be used.
B. Qualifying the Seed Particles
After a plurality of seed particles having the desired shape, size
and color have been produced, the next step is to qualify the seed
particles themselves by subjecting them to inspection by an
automated inspecting and sorting system (100). The qualification
process is necessary to ensure that the color and other
characteristics of the thus-formed seed particles are of sufficient
quality to accurately mimic those of undesirable particles.
Furthermore, the seed particles should be reliably detected by an
automated inspecting and sorting system which is operating under
standard conditions.
An exemplary flowchart showing the overall process for producing
seed particles, imparting the desired color(s) and then qualifying
the seed particles is provided in FIG. 2. The production of
particles and the formation of a conformal surface layer are
summarized in steps S10 through S12. Initially, in step S10 a
plurality of particles of the desired shape, size range, and
composition are produced. In step S11, the particles are screened
via the appropriately sized mesh to separate out those particles
having the desired size distribution. A surface layer is then
formed on the particles in step S12 to yield coated seed particles.
Separate batches may be processed simultaneously in step S12 to
produce seed particles having different colors. In step S13, the
coated seed particles are submitted to the automated sorting system
where they are sorted in step S14. The sorting process is generally
done by submitting seed particles of a single color at a time.
An automated inspecting and sorting system itself has previously
been described with reference to FIG. 1 and is preprogrammed to
accept particles whose color falls within a predetermined range and
then to reject the particles if their color is outside the
acceptable range. In one embodiment, the individual colors or
ranges of colors that are deemed acceptable are set using color
values obtained from actual undesirable particles. These colors
values are loaded into the automated sorting system and used to
determine which particles qualify to be used as seed particles.
Particles whose color falls outside the acceptable range are
rejected and may be retained and used as seed particles in step
S15. If the particles are not rejected and, hence, pass through the
sorting system, they may optionally be inspected and resubmitted to
the automated sorting system in step S16 or they may be discarded
in step S17. If any flaws in the surface layer are found after the
first pass through the automated sorting system, in some
embodiments the seed particles may be repaired and then
reintroduced to the automated sorting system for further testing.
Particles which are submitted to the sorter and are not rejected
after two passes are typically discarded. It is conceivable that
seed particles which are rejected by the sorter a first time may
also be resubmitted to provide additional confidence that they are
being properly rejected.
III. Qualifying a System for Inspecting and Sorting Particles
Once a suitable number of seed particles having the desired size,
shape, and range of colors have been qualified, they may themselves
be used to qualify an automated inspecting and sorting system. An
exemplary flowchart showing the sequence of steps followed in a
method of qualifying an automated inspecting and sorting system
using seed particles is provided in FIG. 3. It is to be understood
that the flowchart shown in FIG. 3 is merely exemplary; and
provides an illustrative example which embodies the spirit and
scope of the present invention. Any of a number of variations may
be implemented without deviating from the inventive concept.
Initially a plurality of seed particles having the desired size and
color distribution are produced in step S20 using the procedures
described in Section II above. The seed particles are then
introduced to the automated sorting system where images of
individual seed particles are initially acquired in step S21. The
automated sorting system is then calibrated in step S22 to
recognize the color or range of colors associated with each seed
particle such that particles having that particular color or range
of colors may be identified and rejected. It is generally necessary
to perform the calibration step S22 for each seed color. Those seed
particles having the appropriate properties are used to ensure that
the automated sorting system recognizes and subsequently rejects
those particles (both seed and undesirable particles) having the
appropriate properties.
Once the automated inspecting and sorting system is calibrated, in
step S23 the seed particles may then be introduced to an actual
process stream which is transmitted through the automated
inspecting and sorting system. The seed particles themselves are
typically introduced at random intervals and are included such that
they are evenly distributed throughout the particles contained
within the process stream. The particles are typically transported
along a moving surface such as a conveyor belt and are monitored in
step S24 using one or more image acquisition devices such as a
camera. The calibration process performed in step S22 allows the
automated sorting system to distinguish between acceptable
particles and undesirable particles within the process stream. The
particles are typically distinguished based upon their color which
are identified through the monitoring process. Systems for
capturing an image of the particles as they are transported along a
moving surface, converting the image to a color signal, and then
comparing the color signal to acceptable values are well-known in
the art and have been previously described in detail by others such
as Gigliotti. If a particle's color falls outside an acceptable
user-defined range, then the particle is identified as an
undesirable particle and is removed from the process stream in step
S25.
Once all of the seed particles have been transmitted through the
automated sorting system, in step S26 it is determined whether the
total number of seed particles removed is equal to the number of
seed particles that were introduced to the process stream. If yes,
then this indicates that the automated sorting system is
functioning according to its intended purpose and the calibration
process is determined to be complete in step S27. If it is
determined in step S26 that fewer than all of the seed particles
have been removed from the process stream, then in step S28 the
calibration process may be determined to be incomplete. In this
case the process flow returns to step S22 where the automated
sorting system is recalibrated and steps S23 through S26 are
repeated. In some embodiments, seed particles which are not removed
in step S26 are discarded since they may not be suitable for use in
the process.
When sorting an actual process stream during startup or under
standard operating conditions, the seed particles need to be
distinguished from conventional undesirable particles. In one
embodiment, seed and undesirable particles may be distinguished by,
for example, applying UV paint to the seed particles as described
in Section I above. When inspecting the rejected particles under UV
light, the seed particles will be readily visible and can be
selectively removed and counted.
In some embodiments it may be permissible to sacrifice sorting
accuracy in order to process particles at higher speeds. In this
case it will generally only be necessary to ensure that the sorting
accuracy remains above a predetermined threshold (i.e., a
predetermined recovery percentage). For example, if it is necessary
for the automated sorting system to recover at least 80% of the
seed particles introduced to the process stream, then the
qualification process shown in FIG. 3 need only be performed to
ensure that the fraction of particles recovered remains above 80%.
It is to be noted that the qualification process itself, including
the establishment of a predetermined recovery percentage, is
typically performed for each color of seed particle that is
introduced to the automated sorting system. What constitutes an
acceptable recovery percentage will typically vary, being a
function of the machine performance and the total number of seeds
used in the test.
It will be readily apparent to persons skilled in the art that a
large number of variations may be implemented into the flowchart
shown in FIG. 3 without deviating from the spirit and scope of the
present invention. For example, the rejected particles may be
reintroduced to the process stream so that they may be given a
second or even a third look by the sorting system. Reintroducing
rejected particles into the process stream helps reduce the number
of particles that may be mistakenly rejected by the system. In
another embodiment, seed particles may be added to a process stream
sorted by human inspectors to test the operational efficiency of
the human inspectors.
In another embodiment, more than one sorting apparatus may be used,
with one being provided downstream to the other and with each
having the same or different criteria for sorting particles.
Rejected particles from the first sorter may be sent to the second
sorter for reexamination using a different set of criteria. Process
parameters that may be varied between a first and second sorter
include, for example, the feed rate, transport speed, the range of
acceptable colors and the imaging conditions. The feed rate is
typically controlled by a feeder which controls the amount of
material fed to a sorter in units of mass (pounds or kilograms) per
hour. The transport speed is generally controlled by varying the
speed of the moving surface such as a conveyor belt (e.g., the belt
speed). As noted above, the transport speed may have a value of,
for example, 480 ft/min or 600 ft/min. The transport speed used is
typically controlled using the system software.
An example of a system which includes a first and second sorter is
provided by the flowchart shown in FIG. 4. In this embodiment,
Feeder #1 initially supplies metal particles to Sorter #1 at Feed
Rate #1. Sorter #1 then processes the particles at Transport Speed
#1. Particles which pass through and, hence, are accepted by Sorter
#1 are sent to a Bin where they may be subject to the next step in
the manufacturing process. The rejected particles from Sorter #1
are sent to Feeder #2 where they are then fed to Sorter #2 at Feed
Rate #2 which, in a particular embodiment is less than Feed Rate
#1. Sorter #2 then processes the particles at Transport Speed #2.
Particles which pass through and, hence, are accepted by Sorter #2
are sent back to Feeder #1 so that they may be reintroduced to
Sorter #1. Rejects from Sorter #2 are subject to visual inspection
where they are either rejected or accepted and sent to the Bin.
By using the process flow shown in FIG. 4, the process stream can
initially be sorted at a relatively high feed rate by Sorter #1
which typically produces a larger number of rejected particles. The
rejected particles can then be resorted at a slower feed rate using
Sorter #2 with the accepted particles being sent back to Feeder #1
while the rejected metal particles from Sorter #2 are visually
inspected and, in some instances, subjected to chemical analysis.
Particles that pass visual inspection are sent to the Bin while
those particles that fail the visual and/or chemical inspection are
typically discarded or subject to further analysis.
Another example of a process flow which utilizes more than one
sorting apparatus is provided in FIG. 5. In this embodiment the
particles are initially sent from Feeder #1 to Sorter #1 at Feed
Rate #1 where the particles are then processed by Sorter #1 at
Transport Speed #1. Particles which pass through and, hence, are
accepted by Sorter #1 are sent to the Bin. The rejected particles
from Sorter #1 are sent to Feeder #2 where they are then fed to
Sorter #2 at Feed Rate #2. The particles are then processed by
Sorter #2 at Transport Speed #2. Although the feed rates used may
be any suitable value, in a particular embodiment, Feed Rate #2 is
less than Feed Rate #1. In this embodiment, rather than being sent
back to Feeder #1, those particles which pass through and, hence,
are accepted by Sorter #2 are sent to the Bin. Rejects from Sorter
#2 are also subject to visual inspection and/or chemical analysis
where they are either rejected or accepted and send to the tote.
The use of a second sorter to inspect the rejects from the first
sorter at a slower feed rate increases both the overall sorting
accuracy and speed.
IV. Exemplary Embodiments
Exemplary embodiments in which actual seed particles are produced
and inspecting and sorting systems are tested are provided.
Although the examples provided in this section involve the
production of Ti seed particles and their use to inspect and sort
Ti sponge, it is to be understood that the methods may find
applications with any type of particle including, for example,
ceramics, polymers, gemstones, metal or ore particles.
Example #1
Ti sponge fragments which were sieved to an 8 mesh size were
anodized in a solution of 10% sodium bicarbonate (NaHCO.sub.3) and
water at room temperature to form an oxide layer having a targeted
thickness. The Ti sponge particles were allowed to sit on a
titanium plate contained within solution. A metal cathode was
immersed in the electrolyte and a direct current was applied
between the electrodes. One batch of Ti sponge fragments was
anodized at an applied voltage of 52 volts (V) for 20 minutes (min)
while a second batch was anodized at 22 V for 20 min. A dark
black/blue surface layer was produced on the surfaces of the Ti
sponge fragments anodized at 52 V as shown, for example, in FIG. 6A
The ruler on the right in FIG. 6A is in centimeters (cm) and
provides a reference framework. Ti fragments having a dark
black/blue color represent the most severe oxidation or nitridation
that may occur during the manufacture of Ti sponge particles. The
Ti sponge fragments anodized at 22 V are shown in FIG. 6B These
seed particles exhibited a lighter color which is more typical of
nitride particles found under standard processing conditions.
Example #2
An Optyx Model 3755 sorting machine which operates in a manner
analogous to the sorting system illustrated in FIG. 1 was mounted
on a small platform and a loss-in-weight type feeder was used to
feed Ti sponge to the sorting machine. Feed rates ranging from 900
to 2,100 pounds (lbs) per hour (h) were used. The system was
configured such that a conveyor belt transports the Ti particles at
approximately 480 feet per minute. Both the upper and lower camera
was used to image the process stream as it was transported on the
conveyor belt. The upper camera faced the belt used to convey Ti
sponge particles whereas the lower camera faced a line of blue
light emitting diodes (LEDs). The Optyx system was operated using
the Key Technology software package, "Keywear 2.01."
A lot comprised of 5 mesh (4 mm) Ti sponge along with two drums of
5 mesh scrap-grade Ti sponge were used for initial tuning
experiments. The sorting process was initiated by loading
undesirable particle types into the computerized vision system.
Undesirable particle types were loaded by feeding samples of
undesirable particles from a library which has been formed and is
continually updated based upon known undesirable particles that
have been identified by the automated inspecting and sorting
system. Samples of black rubber, wood, paper, off-color sponge,
burnt sponge, plastic and a variety of other undesirable particles
were loaded into the system. The smallest undesirable particle that
could be successfully loaded corresponded to three pixels. The line
scan camera used in the sorting machine had a 1024 pixel scan
length and scans were taken at a rate of approximately 4,000 times
per second. Each pixel measured approximately 0.02 inches (0.5 mm)
on a side. Once a type of undesirable particle was loaded into the
database, it was given an identifying name. Different undesirable
particle classes or types can be activated or deactivated in the
sorting machine as needed.
Seed particles were produced using 0.25 inch Ti cubes which were
anodized to produce seed particles having a dark yellow-golden
color and which resemble Ti.sub.1-xN.sub.x samples having 22%
nitrogen ("22% TiN"). A total of fifteen anodized 0.25-inch Ti
cubes were added to the batch of 5 mesh Ti sponge to determine the
sorting machine's ability to detect the Ti seed particles. An
identical test was performed using actual 22% TiN samples of burnt
Ti sponge to serve as a basis for comparison. The test results are
provided in Table 1 below:
TABLE-US-00001 TABLE 1 Comparison of sorting tests for Ti seed and
burnt Ti sponge Eject Fired Passed Rejected 1/4 inch Anodized Ti
Cubes 15 1 14 15 0 15 15 0 15 15 0 15 15 0 15 15 0 15 22% TiN 15 0
15 15 0 15 15 0 15 14 1 14 15 0 15
The left column in Table 1 represents the number of seed or
undesirable particles that were added to the process stream, the
central column represents the number of undesirable or seed
particles that passed through the sorting system whereas the right
column indicates the total number of particles that were rejected.
As Table 1 shows, rejection of the anodized Ti cubes occurred at
the same rate as the burnt Ti sponge particles. The identical
rejection rates indicate that anodized 0.25 inch Ti cubes may be
used to test the sorting capability of the system.
Example #3
In this example, a large batch of Ti sponge particles was sorted to
determine the accuracy of the sorting process. A total of
approximately 12,000 lbs of 5 mesh Ti sponge was processed by the
same Optyx Model 3755 sorting machine disclosed in Example 2. Five
separate batches of between 2,700 to 3,800 lbs each were sorted.
Two separate test runs were performed on each individual batch of
Ti sponge particles. The sorting accuracy was measured in two ways.
First, the total weight of undesirable particles removed by the
sorting machine was compared between the two test runs; and second,
the total number of undesirable particles of each type removed by
the sorting machine were compared between the two test runs. In
each test run, the total amount of Ti sponge sent to the
undesirable particle stream was similar between the two test runs
while the Ti sponge was sorted at a feed rate of 1,500 lbs/hr. The
accuracy of the sorting process is measured by dividing the total
number of undesirable particles found during the first sorting test
by the total number of undesirable particles found during the first
and second sorting tests. The results of the sorting process are
summarized in Table 2 below:
TABLE-US-00002 TABLE 2 Undesirable particle type and sorting
accuracy at a 1,500 lb/hr feed rate and a 480 ft/min belt speed
BLEND B-372 B-381 B-358 B-358 B-371 Undesirable Particle Sort
Resort Sort Resort Sort Resort Sort Resort Sort Resort Type (count)
(count) (count) (count) (count) Avg. Rust Colored Sponge 17 10 100
28 86 55 14 3 257 99 Blue colored foil 82 48 23 4 107 34 110 50 100
22 Discolored Sponge 108 1 42 1 2 2 1 5 2 0 Gold Colored Foil 155
80 27 18 794 257 779 416 219 56 Paint Chip 3 0 1 0 0 0 1 0 1 0
Painted Titanium 1 0 7 0 0 0 0 0 0 0 Off Color 10 3 6 4 18 0 2 0 4
6 Crystal/Skin 63 40 261 115 82 65 133 86 97 65 Plastic 6 1 18 8 0
0 0 0 5 0 Mg 1 0 28 2 0 0 0 0 0 1 MgCl.sub.2 1 0 27 6 10 3 7 1 26 7
Silver Foil 139 56 11 3 151 76 139 90 24 120 Wood 4 1 9 0 0 0 0 0
119 8 Unknown 2 0 2 4 1 0 0 1 1 0 Scale 38 3 3 0 6 1 0 1 2 1 Paper
0 7 0 4 0 0 0 66 29 Insect parts 0 0 0 1 0 0 0 1 1 Cigarette 0 1 2
0 0 0 0 0 0 Ferro-ti 0 1 15 9 2 3 6 6 4 RTV 0 1 0 0 0 0 0 1 1
Rubber 0 1 2 1 0 3 0 0 0 Pine needle 0 0 11 0 0 0 0 0 0 Sun flower
seed 0 0 1 1 0 1 0 1 0 Tape 0 0 0 0 1 0 Pounds sorted 13.7 10.92
6.652 1.91 32.3 37.09 36.59 37.82 30.77 33.12 Pounds sorted of 0.7
0.23 0.652 0.196 1.918 0.61 1.769 0.91 0.978 0.426 undesirable
particles Total pounds 3292 2942 3830 3360 2704 Accuracy (rust,
disc, 0.91 0.80 0.65 0.65 0.72 0.75 rubber, off color) Accuracy
(foreign) 0.92 0.78 0.85 0.75 0.82 0.82 Accuracy (blue foil) 0.63
0.85 0.76 0.69 0.82 0.75 Accuracy by weight 0.75 0.77 0.76 0.66
0.70 0.73 Loss rate (%) 0.4 0.3 0.25 0.07 0.9 1.0 1.1 1.2 1.2
1.2
The results provided in Table 2 show that the accuracy of detection
and removal of rust, disc, rubber and off-color samples as averaged
over all five batches was 75%. This means that 75% of these
undesirable particles were removed from the process stream by the
automated sorting system. For foreign matter, the accuracy was 82%,
and for blue foil the sorting system exhibited an accuracy of 75%.
By weight, the overall accuracy of the sorting system was found to
be an average of 73%.
Example #4
In this example, five batches of Ti sponge particles were sorted in
a manner analogous to that described in Example 3. The Ti sponge
was sized using a 5 mesh screen whereas the undesirable particles
were further sized using a 12 mesh screen to remove very fine
particles from the undesirable particle stream. A reduced feed rate
of 1,000 lb/hr was used during the sorting process. The results are
summarized in Table 3 below.
TABLE-US-00003 TABLE 3 Undesirable particle type and sorting
accuracy at a 1,000 lb/hr feed rate BLEND Batch #1 Batch #2 Batch
#3 Batch #4 Batch #5 Undesirable particle Sort ReSort Sort ReSort
Sort ReSort Sort ReSort Sort ReSort Type (count) (count) (count)
(count) (count) Insect/Plant Fiber 2 3 4 3 Wood 1 0 Feather
MgCl.sub.2 16 2 14 2 51 20 5 1 73 8 Mg 0 1 1 1 0 1 Rubber 2 0 84 4
2 0 6 2 85 2 Discolored 12 1 16 0 49 2 6 4 34 4 Blue Foil 6 8 26 12
17 0 35 15 17 7 Yellow Paint White Plastic 1 1 5 1 Paper 1 0 16 5
Scale 1 0 0 1 11 1 Foil 7 4 11 0 0 0 7 5 Gold Foil 22 0 55 29 0 5
31 16 19 0 Unknown 6 0 12 3 0 1 0 Rust Colored Sponge 10 9 3 Rate
(lb/hr) 868 903 666 666 823 856 1533 1022 960 991 Wt 391 391 311
311 357 357 511 511 512 512 Wt Undesirable particle 5.9 4.2 5.2
3.89 5.62 4.46 5.18 2.64 4.7 3.5 Wt-12 mesh 1.6 0.265 2.05 1.25 2.5
1.78 2.32 1.1 2.6 1.5 % undesirable particle (wt) 1.9 1.1 1.1 1.65
2.3 1.75 1.5 0.7 1.4 0.97 Accuracy 0.821 0.802 0.82 0.696 0.903
The results in Table 3 show that the detection accuracy over five
batches of samples ranged from a low of 69.6% to a high of 90.3%.
The average percentage of undesirable particles removed from the
process stream was 80.8%. It is likely that the higher recovery
value can be attributed to the lower feed rate used during this
test run.
Example #5
In this example, a plurality of Ti sponge particles which were
initially screened to produce separate batches of 6, 7, 8, and 12
mesh particles. Each batch was anodized by immersion in a 10%
solution of sodium bicarbonate and applying a direct current at 22
V or 52 V for up to 20 minutes in the manner described in Example 1
to produce Ti seed particles. The thus-formed Ti seed particles
were then painted with fluorescent paint.
After the Ti seed particles were formed, they were individually
tested for color recognition by passing them through an automated
inspecting and sorting system analogous to that described in
Example 2. When the sorting system is properly configured, there is
substantially a 100% rejection of the 6 and 8 mesh blue and 8 mesh
red Ti seed particle. Under standard operating conditions about
half (50%) of the 12 mesh blue Ti seed particles are rejected
whereas only a small fraction of the 7 mesh gold Ti seed particles
were rejected. The smaller rejection rate of the 12 mesh blue Ti
seed particles is due to their small size whereas the low rejection
rate of gold Ti seed particles is due to the difficulty in
producing adequately colored gold Ti seed particles. The size,
color and number of Ti seed particles used in this example are
listed in Table 4 below.
TABLE-US-00004 TABLE 4 Ti seed particle sizes and colors Size Color
Seed count 6 mesh Blue 5 7 mesh Gold 5 8 mesh Blue 10 8 mesh Red 10
12 mesh Blue 10
Ti seed particles were then used to determine the recovery rate of
an automated inspecting and sorting system analogous to that
described in Example 2 and shown in FIG. 1. In this example, the
operation of an automated inspecting and sorting system having the
configuration shown in FIG. 5 was tested by first sorting a batch
of Ti sponge particles at a first feed rate and then resorting the
rejected particles from that same batch using the same sorting
system which is operated at a second feed rate.
The Ti seed particles are added to individual batches of Ti sponge
particles at random intervals and then subject to inspection by the
automated sorting system. The first sort is performed at high
speed, using a nominal feed rate of 3,400 lb/hr. The instantaneous
feed rate would vary between 2,700 to 3,700 lb/hr, but would
typically remain steady at a rate of about 3,400 lb/hr. The
rejected particles from this initial sorting run were then retained
and resubmitted to the automated sorting system for a second sort
at low speed, using a feed rate of 1,000 lb/hr. The actual feed
rate would vary from a low of 920 to a high of 1,100 lb/hr, but was
maintained at a nominal value of 1,000 lb/hr. The rejects from the
second sort were then observed under a black light and the Ti seed
particles were recovered. The recovery rate obtained for five
separate batches of Ti sponge particles (Batch Nos. A1-A5) which
were processed by the automated inspecting and sorting system is
provided in Table 5 below.
TABLE-US-00005 TABLE 5 Ti seed particle recovery (%) by automated
inspecting and sorting system using a first sort at 3,400 lb/hr and
a second sort at 1,000 lb/hr. Ti Seed Particle Recovery Rate (%) 6
mesh 7 mesh 8 mesh 8 mesh 12 mesh Batch No. Blue Gold Blue Red Blue
A1 80% 80% 60% 70% 40% A2 40% 60% 70% 100% 40% A3 80% 80% 100% 70%
40% A4 60% 80% 70% 70% 60% A5 60% 100% 80% 90% 50% Average 64% 80%
76% 80% 46%
Recovery rates measured ranged from 64% for 6 mesh blue Ti seed
particles, 80% for 7 mesh gold Ti seed particles, 76% for 8 mesh
blue Ti seed particles, 80% for 8 mesh red Ti seed particles, to
46% for 12 mesh blue Ti seed particles. The highest recovery rate
measured by automated inspection was for the 7 mesh gold Ti seed
particles whereas the lowest recovery rates were for the 12 mesh
blue Ti seed particles.
The recovery rates obtained for each class of Ti seed particles are
plotted in FIG. 7 to provide a basis for comparison. Within FIG. 7,
the label "o" represents the automated sorting system. The numbers
6, 7, 8, and 12 represent 6, 7, 8, and 12 mesh seed particles,
respectively, whereas the letters b, g, and r represent blue, gold,
and red particles, respectively. Thus, as an example, the label O6b
represents the recovery rate obtained for automated inspection of 6
mesh blue Ti seed particles. Within FIG. 7, the vertical bars
represent the extent of the entire range of recovery rates achieved
for that particular sorting process whereas the vertical boxes
represent a 90% confidence level in the data based on a normal
distribution of the data. The results provided in Tables 4 and 5
and illustrated in FIG. 7 suggest the viability of using anodized
Ti sponge as seed particles to periodically qualify an automated
inspecting and sorting system.
The recovery rates of Ti seed particles obtained for automated
inspecting processes were also calculated based upon the weight of
the Ti seed particles. This was obtained by measuring the total
weight of the Ti seed particles added to each batch and then
measuring the weight of the recovered Ti seed particles. The weight
percent (wt. %) recovery was calculated by dividing the weight of
the recovered Ti seed particles by the total weight of all Ti seed
particles added and multiplying the result by 100. The results are
provided in Table 6 below for the same five batches of Ti particles
analyzed in Tables 4 and 5. In Table 6, the batch number is
provided at the left whereas "Batch weight" represents the total
weight of all Ti particles and Ti seed particles contained within a
batch. The "Primary rejects" and "Secondary rejects" respectively
represent the weight percent of particles (as a function of the
batch weight) which were recovered after completion of the first
and second sorting operation performed by the automated inspecting
and sorting system. Seed particles were identified by visual
overcheck where a UV coating permitted location of these particles
by UV light in a darkened room.
TABLE-US-00006 TABLE 6 Rejection weights and seed recovery weights
Secondary Batch Batch Primary rejects rejects Recovery of No.
weight (lb) (wt. % of total) (wt. % of total) Seeds (wt. %) 1 3193
21.7 5.7 62.0 2 3093 19.2 3.7 62.9 3 2622 19.0 3.5 75.1 4 3241 21.0
5.1 73.0 5 2695 22.1 5.1 72.3 Average -- 20.6 4.62 69.1
The results in Table 6 show that the primary rejects amount to 19.0
to 22.1 wt. % of the total batch weight whereas the secondary
rejects represent 3.5 to 5.7 wt. % of the total batch weight. Thus,
the automated inspecting and sorting system concentrates the
detected undesirable particles to an amount representing 3.5 to 5.7
wt. % of the total weight of Ti sponge particles processed. The far
right columns in Table 6 provide the wt. % of Ti seed particles
recovered by automated sorting of the process stream.
As the above Examples show, by using seed particles to quantify the
sorting capability of an automated inspecting and sorting system,
the accuracy of the system may be tested and verified. By
periodically quantifying their sorting capabilities, the continued
proper operation of the sorting system can be verified.
It will be appreciated by persons skilled in the art that the
present invention is not limited to what has been particularly
shown and described hereinabove. Rather, the scope of the present
invention is defined by the claims which follow. It should further
be understood that the above description is only representative of
illustrative examples of embodiments. For the reader's convenience,
the above description has focused on a representative sample of
possible embodiments, a sample that teaches the principles of the
present invention. Other embodiments may result from a different
combination of portions of different embodiments.
The description has not attempted to exhaustively enumerate all
possible variations. The alternate embodiments may not have been
presented for a specific portion of the invention, and may result
from a different combination of described portions, or that other
undescribed alternate embodiments may be available for a portion,
is not to be considered a disclaimer of those alternate
embodiments. It will be appreciated that many of those undescribed
embodiments are within the literal scope of the following claims
and others are equivalent. Furthermore, all references,
publications, U.S. patents, and U.S. patent application
Publications cited throughout this specification are hereby
incorporated by reference as if fully set forth in this
specification.
* * * * *
References